The Palestinian-led Boycott, Divestment, Sanctions movement (BDS) tries to put economic and political pressure on Israel, but many pro-Israel advocates say the campaign ultimately aims to undermine the country's security and financial stability. Now, new legislation in the United States Congress could make it illegal for businesses in the US to participate in BDS activity.

According to the American Civil Liberties Union, a civil liberties organisation, the bipartisan Israel Anti-Boycott Act proposes to penalise support for boycotts of Israel or its businesses, with violations punishable by penalties of up to $1 million and 20 years in prison. In the US, at least 20 states have already adopted legislation targeting BDS involvement, or issued executive orders that prohibit state agencies from contracting with businesses engaged in similar activity.

Supporters of BDS contend that the movement is a successful expression of their freedom of speech as protected under the First Amendment to the US Constitution, which is why opponents have shifted to "legal warfare". BDS co-founder Omar Barghouti says this is because Israel and "its massive lobby" are "losing so many battles" in the court of public opinion.

In October, the ACLU filed a federal lawsuit in the state of Kansas challenging anti-BDS bills, claiming that boycotts are protected under the First Amendment. But proponents of anti-BDS legislation say there's nothing "unconstitutional" about such measures, adding that they're in-line with an established US law that penalises corporations that "participate in boycott requests from foreign countries against US allies". Mark Levenson, chair of the New Jersey State Association of Jewish Federations, says BDS is "one of the greatest canards" of the 21st century, and that its supporters should be "condemned vigorously and publicly, roundly and soundly".

"You can boycott Israel. That's your choice…But if you do, we will look to have [New Jersey] disinvest in you."

So, what are the legal underpinnings of anti-BDS legislation, and what are the possible consequences for companies supporting BDS?